FC5: X-Forwarding through ssh-tunnel

Hi,

i'm trying to tunnel the graphical output of a program through a restrictive 
firewall using ssh-tunnel.

I enabled X-Forwarding in /etc/ssh/sshd_config on the remote machine (Debian sarge)

...
X11Forwarding yes
X11DisplayOffset 10
...

and connected with ssh -X but whenever i try to start a program:

vdr:~# export DISPLAY=localhost:10.0
vdr:~# easytag

(easytag:6517): Gtk-WARNING **: cannot open display:
vdr:~#

I cannot find anything in the logifles on my local machine.
Do i need some additinal configuration on my local FC5 machine to get this working?

Thanks,

Andre